1. Field of the Invention
The present invention relates to workpiece mounting devices and, more particularly, to a device for mounting workpieces that facilitates their treatment by a fluid mixture.
2. Brief Description of Related Developments
Designs for treating workpieces, such as for example, wafers or parts to be cleaned, in a fluid mixture generally use active stirring mechanisms physically separate from the workpiece mounting. In thin film processing, cleaning and other processes, it is generally desirable to have flow directed axially with respect to the surface of the workpiece.
In the process of fabricating a semiconductor device, a predetermined pattern is transferred to or drawn on a resist film covering the surface of a semiconductor substrate. The fabrication process uses water and aqueous bases for developing or rinsing the created photoresist pattern, and rinsing off strippers and slurries. The remaining surface liquid, such as water, can cause a collapse of the resist pattern during the evaporation of the surface liquid. This image collapse is due to the high surface tension of the surface liquid.
In order to reduce image collapse, liquified, or supercritical, carbon dioxide (SCCO2) having a very low surface tension is mixed with the surface liquid remaining on the semiconductor device to remove the surface liquid from the semiconductor device. As carbon dioxide is not very soluble in water, an additional emulsifying agent, or agents, can be added to the liquified carbon dioxide to aid in inducing a low surface tension in the water. The additional agent needs to be mixed with the liquified carbon dioxide, or the combination of the liquified carbon dioxide and the agent, must be mixed with the surface water. While some mixing methods have been used to stir the liquified fluid with the surface liquid, image collapse due to the high surface tension is still a problem. In addition, reducing image collapse is becoming more important as semiconductor devices become larger with more complex resist patterns, and the resist patterns are including patterns of lines and spaces which are decreasing in size.
It would be advantageous to be able to facilitate the processing of semiconductor devices with a liquified fluid mixture and provide fluid agitation for mixing and directed flow into a single part.
The present invention is directed to a workpiece holder for processing a workpiece in a chamber of a liquified fluid. In one embodiment, the workpiece holder includes a cylindrically shaped rotator having an exterior wall and at least one fluid guide on the exterior wall. The rotator is adapted to rotate and provide fluid flow across a first end of the rotator, and is adapted to provide fluid flow and mixing perpendicular to a surface of the first end of the rotator. A fixture is coupled to the first end of the rotator for securing the workpiece to the first end of the rotator.
In one aspect, the present invention is directed to a method of processing a workpiece in a chamber of liquified fluid. In one embodiment, the method includes providing a workpiece holder including a cylindrically shaped rotator having an exterior wall and at least one fluid guide on the exterior wall, the rotator adapted to rotate and provide fluid flow across a first end of the rotator. The step of providing the workpiece holder also includes a fixture coupled to the first end of the rotator for securing the workpiece to the first end of the rotator. The method further includes securing the workpiece to the first end of the cylindrically shaped rotator with the fixture, and rotating the workpiece holder, wherein the at least one fluid guide mixes and agitates the liquified fluid and directs the liquified fluid perpendicular to a surface of the first end of the rotator to remove surface fluid from the workpiece and preventing image collapse of the workpiece.